I'm trying to avoid seams when tiling a surface with textures from texture atlas (the problem and possible solution can be found here: http://mtnphil.wordpress.com/2011/09/22/terrain-engine/)
I need to manually calculate mipmap level in GLSLES fragment shader and thus use texture2DLod() function.
Here is my fragment shader:

According to my googling, texture2DLod can be used in fragment shader (though OGL specs say it should be used only in vertex shader - maybe a misprint).
I've tried defining extensions such as GL_EXT_shader_texture_lod, but none of them are accepted by the shader compiler.

Did I go wrong somewhere, or texture2DLod() is just supported by a narrow range of hardware?

My videocard is GeForce N210, also I tried my app on Samsung GalaxyTab with no result.